1. Field of the Invention
The present invention relates generally to an apparatus and method for separating solids from a fluid and more particularly, but not by way of limitation, to an apparatus for separating solids from a drilling fluid and treating the removed solids allowing for ecologically safe disposal of the solids.
2. Brief Description of Related Art
Drilling fluids are typically utilized in oil and gas drilling operations. Drilling fluids such as water, air, polymers or combinations thereof are pumped through the drill string, out of the drill bit, into the annulus that surrounds the drill string. The drilling fluid returns to the surface carrying with it crushed rock and other solids.
Special care must be taken to process the drilling fluid and solids so as to avoid pollution caused by pumping drilling fluid and solids directly into the environment. Also, separating the solids from the drilling fluid allows the rig operators to recycle the drilling fluid and lower the cost of operating the rig.
Solids are generally removed from drilling fluid by processes involving machinery known as shale shakers. Typical shale shakers comprise large, flat sheets of wire mesh or sieves of varying sizes. Drilling fluid and solids are deposited onto the wire mesh and/or sieves. The shale shakers are then vibrated to separate the solids from the drilling fluid. The drilling fluid is collected and pumped back into the well for continued use.
Although shakers remove solids from drilling fluid, a substantial amount of solids may remain suspended in the drilling fluid. Solids left in the drilling fluid can, over time, cause bridges and fill which may result in what is generally known as stuck-pipe and lost circulation. High concentrations of solids in drilling fluid may lead to drilling inefficiencies due to increased weight and viscosity of the drilling fluid which, in turn, leads to a need for increased dilution of the drilling fluid. Diluting the drilling fluid is undesirable as diluting the drilling fluid alters the viscous properties of the drilling fluid. Also, solids suspended in the drilling fluid may be detrimental to the rate of penetration of the drill bit due to increased viscosity of the drilling fluid leading to an increase in horsepower required to circulate the drilling fluid within the well. Solids which are not removed in the first pass through the shakers are re-circulated into the well where these non-removed solids are further broken down into finer sediment which is increasingly difficult to remove.
Once the solids are removed, the well operator must often contend with natural gases or other flammable material contained within the solids that pose a significant risk of explosions and fire. Therefore, solids must be stabilized with a treatment material which neutralizes the volatility of the solids. Examples of treatment material may include fly ash, lime, cement, gypsum, or combination thereof. The solids and treatment material are mixed together until fully incorporated and the mixture is then transported to a solids pit.
Due to the many steps and machinery involved in thoroughly separating solids from drilling fluid, it is common place for the separation of solids from drilling fluid to be extremely costly and time consuming. Therefore, what is needed is an apparatus and method for removing a substantial amount of solids from drilling fluid and also treats the removed solids for proper ecologically sound disposal. It is to such an apparatus that the present invention is directed.